Jason Jia: How is the kilogram being defined?
The kilogram is defined as being equal to the mass of the International Prototype Kilogram (IPK), which is almost exactly equal to the mass of one litre of water.
Jason Lim:
Kho Wen Hao:
Samuel Kng:
Koh Han Wei: How was the kilogram being defined and how did it evolve?
The gram was decreed to be equal to the mass of water in a centimeter cube, at waters melting point, 0°C, in France, on the 7th April 1795. They took the concept from the English Philosopher, John Wilkins, in 1668, when he thought of using a unit to define a mass. However, since trade usually handled objects a few hundreds of folds larger than a gram, they decided to make the kilogram, a more standard measurement used.
It was soon realized that the definition of the original gram using 0 °C was highly unstable. Hence, two scientists, French chemist Louis Lefèvre-Gineau and Italian naturalist Giovanni Fabbroni, spent several years researching to increase the accuracy of the definition. 4 years after the first definition was placed, a new definition took over. They changed the temperature relative to the density from 0°C to 4°C, where water was supposedly the densest. They still realised that the old kilogram definition was a tad inaccurate, where a thousand cubic centimeters of water at its maximum density was 99.93% the target mass of the standard kilogram. The same year, a kilogram of pure platinum prototype was made the closely resemble the best definition. The standard of these two brilliant scientists stood for another ninety years.
The kilogram is defined as being equal to the mass of the International Prototype Kilogram (IPK), which is almost exactly equal to the mass of one litre of water.
Jason Lim:
Kho Wen Hao:
Samuel Kng:
Koh Han Wei: How was the kilogram being defined and how did it evolve?
The gram was decreed to be equal to the mass of water in a centimeter cube, at waters melting point, 0°C, in France, on the 7th April 1795. They took the concept from the English Philosopher, John Wilkins, in 1668, when he thought of using a unit to define a mass. However, since trade usually handled objects a few hundreds of folds larger than a gram, they decided to make the kilogram, a more standard measurement used.
It was soon realized that the definition of the original gram using 0 °C was highly unstable. Hence, two scientists, French chemist Louis Lefèvre-Gineau and Italian naturalist Giovanni Fabbroni, spent several years researching to increase the accuracy of the definition. 4 years after the first definition was placed, a new definition took over. They changed the temperature relative to the density from 0°C to 4°C, where water was supposedly the densest. They still realised that the old kilogram definition was a tad inaccurate, where a thousand cubic centimeters of water at its maximum density was 99.93% the target mass of the standard kilogram. The same year, a kilogram of pure platinum prototype was made the closely resemble the best definition. The standard of these two brilliant scientists stood for another ninety years.
Reference:
http://en.wikipedia.org/wiki/Kilogram#History